The bark from sawmill processes is underutilized in many wood processing regions, causing confinement and environmental problems. This article aims to determine the proportion of bark to add to pine sawdust in the manufacture of pellets without reducing their quality as well as to identify the biomass and pelletization process variables related to pellet quality parameters. The pellets were produced using blends of sawdust and bark from Pinus durangensis at bark percentages of 50, 60, 70, 80, 90, and 100 at moisture levels of 9% and 12%. Particle size distribution, proximate analysis, and gross calorific values of all biomass blends were determined; for pellets in addition to the earlier, it was also determined bulk density and hardness. Statistical analyses were conducted to assess how the proportion of bark in the blends affects both material properties and pellet quality. In addition, the effect of the bark percentage in the blends on various biomass properties and pellet quality parameters was analyzed using multivariate analysis. All bark-sawdust blend pellets meet the ISO 17225-2 class A requirements for the moisture content (≤12%) and the ash content. The 90% and 100% bark blends meet bulk density requirements at both moisture content levels, while all evaluated complied with the hardness. Overall, biomass properties—particularly bark content, ash, fixed carbon, and particle size—directly dictate pellet quality, significantly influencing the gross calorific value, bulk density, and mechanical durability of the final biofuel.
Carrillo-Parra et al. (Sun,) studied this question.